The invention relates generally to the field of injection systems for compression ignition engines and more particularly to a constant high pressure, electronically controlled fuel injection system for delivering fuel through valve or gate type injectors.
Those skilled in the art are aware that hitherto known mechanically actuated or mechanically operated injection systems have numerous problems which affect engine performance characteristics. One such problem is the fixed time of injection; and another is the lack of ability to vary the amount of fuel injected with respect to engine speed and/or load. Still another is the pressure under which fuel is injected inasmuch as pressure is a function of the speed of the engine. As a result, such known systems impose constraints on the engine which are decidedly detrimental. Among these are vibrations, unfavorable burning characteristics of the fuel over a wide range of the engine speed range, and poor emissions management to name the most obvious. So far as the burning characteristics of the fuel are concerned, such known systems affect the completeness of the combustion, flame propagation burning characteristics and flame speed. There are few systems which depart from the basic undesirable design deficiencies of mechanical systems and even these depart only from some of those deficiencies. A jerk pump type system, for instance, is pressure differential actuated and while it approaches constant pressure it is not high pressure, and does not vary the time at which injection is begun with sufficient advance for higher engine speeds nor does it vary the amount of the fuel injected from cycle to cycle. Cam timed injection systems involve pressures generated within the injector, but the pressures attained are dependent on the speed of the engine. Neither system is able to respond to variable engine demands in accordance with speed and load. The net result of the known systems is that there is only a small portion of the total operating engine range in which the engine operates efficiently. In otherwords, there is a very slight percentage of engine speed at which the engine will run with optimum efficiency. To sum up, mechanical systems have an injection timing constant, that is, the instant and duration of fuel injected and the constraints this constant imposes are recognized deficiencies.
Among the prior art references to be considered are the following: U.S. Pat. Nos. 3,430,616; 3,913,536; 3,752,137; 3,653,365; and 3,587,547.